Stephanie McGuire, 21, was taken into custody after allegedly breaking in to the school on October 8.
She and 21-year-old Stephanie Bristol are accused of stealing electronic gear and then selling it to a pawn shop.
According to detectives, the girls entered Farmingdale High School through an open door and removed a Kindle tablet and digital electronic scales from multiple classrooms.
The investigation determined that Bristol had entered the school on September 25 and removed five calculators that were also recovered from the same pawn shop.
Bristol was arrested on October 11 at her residence.
Both women are charged with burglary and criminal possession of stolen property.